Optical path control device and display device

Abstract

This invention relates to an optical path control device and a display device, such that the visual perception of the image output when an optical section based on a first axis swings is the same as that of the image output when an optical section based on a second axis swings, thereby suppressing image quality degradation. It includes: a swinging section having: an optical section for light incidence; a first swinging section supporting the optical section; and a second swinging section supported by the first swinging section via the first axis and supported by the second swinging section via the second axis; a first actuator for swinging the swinging section about the first axis as a fulcrum and about a first swinging axis including the first axis as a center; and a second actuator for swinging the swinging section about the second axis as a fulcrum and about a second swinging axis including the second axis as a center, wherein the first and second swinging axes intersect, and the torsional stiffness of the second axis is higher than that of the first axis.

Description

Technical Field

[0001] This invention relates to an optical path control device and a display device. Background Technology

[0002] Optical devices are known to deflect the optical axis by oscillating the optical section into which light is incident. For example, Patent Documents 1 and 2 describe a technique in which the optical path of light passing through the optical section is deflected by oscillating the optical section, thereby enabling the resolution of the projected image to be higher than that of the optical modulation device.

[0003] Prior art literature

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2016-071232;

[0006] Patent Document 2: Japanese Patent Application Publication No. 2020-077911. Summary of the Invention

[0007] The problem that the invention aims to solve

[0008] Optical devices are known that deflect the light path of light passing through the optical unit by oscillating the optical unit around intersecting first and second axes. In such devices, there are cases where an image is displayed during the oscillation of the optical unit. In this case, if the oscillation time of the optical unit based on the first axis differs from that based on the second axis, the visual perception of the image output during the oscillation of the optical unit based on the first axis differs from that of the image output during the oscillation of the optical unit based on the second axis, resulting in degraded image quality. Therefore, it is necessary to implement measures such as not displaying the image during the displacement of the optical unit, and displaying the image after the displacement ends and stabilizes. However, if the displacement speeds based on each axis are different, the image display time differs for each axis, leading to the problem that modulation control becomes more complex by requiring adjustments to modulation control based on the image display time to optimize image display.

[0009] In optical devices, a drive unit applies a drive signal to an actuator to drive the actuator, causing the optical component to oscillate. The waveform of the drive signal output by the drive unit is pre-adjusted to a predetermined waveform. However, for example, during the assembly of optical devices, the inherent frequency of the oscillating component may change due to factors such as misalignment of the components, changes over time, and ambient temperature. In such cases, it becomes difficult to readjust the waveform of the drive signal.

[0010] In view of the above-mentioned problems, one object of the present invention is to provide an optical path control device and a display device such that the visual perception of the image output when the optical part based on the first axis swings is the same as that of the image output when the optical part based on the second axis swings, thereby suppressing the degradation of image quality.

[0011] In view of the above-mentioned problems, another object of the present invention is to provide an optical path control device and a display device that automatically adjust the waveform of the drive signal used to drive the actuator, thereby reducing the working time.

[0012] means for solving problems

[0013] One aspect of the present invention relates to an optical path control device, comprising: a swinging part having: an optical part for light incident; a first swinging part supporting the optical part; and a second swinging part supported on a support part by a second shaft, the first swinging part being supported on the second swinging part by a first shaft; a first actuator causing the swinging part to swing about the first shaft as a fulcrum and about a first swinging axis including the first shaft as a center; and a second actuator causing the swinging part to swing about the second shaft as a fulcrum and about a second swinging axis including the second shaft as a center, the first swinging axis intersecting the second swinging axis, the torsional stiffness of the second shaft being higher than the torsional stiffness of the first shaft.

[0014] One aspect of the present invention relates to a display device comprising the aforementioned optical path control device and an illumination device for illuminating light onto the optical portion.

[0015] Invention Effects

[0016] According to the present invention, the visual perception of the image appearing when the optical part based on the first axis swings is the same as that of the image appearing when the optical part based on the second axis swings, thereby suppressing the degradation of image quality.

[0017] According to the present invention, the waveform of the drive signal used to drive the actuator can be automatically adjusted, thereby reducing the working time. Attached Figure Description

[0018] Figure 1 This is a schematic diagram illustrating the display device according to the first embodiment;

[0019] Figure 2 It is a block diagram schematically representing the circuit structure of a display device;

[0020] Figure 3 This is a top view showing the optical path control mechanism;

[0021] Figure 4 yes Figure 3Section IV-IV;

[0022] Figure 5 yes Figure 3 VV cross-sectional diagram;

[0023] Figure 6 This is a three-dimensional view showing the swinging part in the optical path control mechanism;

[0024] Figure 7 It is a graph illustrating the waveform of the drive signal of the drive unit;

[0025] Figure 8 It is a graph illustrating the single-axis oscillation mode of the optical section;

[0026] Figure 9 This is an explanatory diagram illustrating the dual-axis oscillation mode of the optical section;

[0027] Figure 10 It is a graph illustrating the biaxial oscillation mode when the natural frequencies of the first and second shafts are different;

[0028] Figure 11 It is a graph illustrating the biaxial oscillation mode when the natural frequencies of the first and second shafts are the same.

[0029] Figure 12 This is a cross-sectional view showing the optical path control mechanism according to the second embodiment;

[0030] Figure 13 It is a block diagram that schematically represents the circuit structure of a display device. Detailed Implementation

[0031] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the present invention is not limited to the embodiments described below.

[0032] <First Implementation Method>

[0033] [Brief Structure of the Display Device]

[0034] Figure 1 This is a schematic diagram of a display device according to the first embodiment.

[0035] In the first embodiment, such as Figure 1 As shown, the display device 1 includes a light path control device 10 and an illumination device 100. The illumination device 100 is a device for illuminating an image with light L. The light path control device 10 is a device for controlling the light path of light L. By shifting the optical axis of light L, the light path control device 10 shifts the position of the image displayed by light L, thereby making the resolution of the projected image greater than the resolution of the image of the illumination device 100 (i.e., the number of pixels of the display element 106, described later).

[0036] The illumination device 100 includes a light source 101, polarizing plates 105R, 105G, and 105B, display elements 106R, 106G, and 106B, polarizing plates 107R, 107G, and 107B, a color combining prism 108, a projection lens 109, dichroic mirrors 120 and 121, reflectors 130 and 131, lenses 140, 141, 142, 143, 144, and 145, a polarization conversion element 150, and an image signal processing circuit 160. Display elements 106R, 106G, and 106B are referred to as display element 106 without distinction.

[0037] Light source 101 is a light source that generates and illuminates light. Light source 101 illuminates incident light L0. In the following description, one light source 101 will be used as an example to illuminate incident light L0, but other optical devices for generating incident light L0 may also be used.

[0038] Incident light L0 from light source 101 is incident on lens 140. Lenses 140 and 141 are, for example, compound eye lenses. Lenses 140 and 141 homogenize the illumination distribution of the incident light L0, which is then incident on polarization conversion element 150. Polarization conversion element 150 is an element that unifies the polarization of the incident light L0, for example, having a polarization beam splitter and a phase difference plate. Polarization conversion element 150, for example, unifies the incident light L0 with p-polarized light.

[0039] The incident light L0, after being polarized by the polarization conversion element 150, illuminates the dichroic mirror 120 via the lens 142. The lens 142 is, for example, a condenser lens.

[0040] Dichroic mirror 120 separates the incident light L0 into yellow light LRG and blue light LB, which contains a blue band component. The yellow illumination light LRG, separated by dichroic mirror 120, is reflected by mirror 130 and incident on dichroic mirror 121.

[0041] Dichroic mirror 121 separates the incident yellow light LRG into red light LR containing a red band component and green light LG containing a green band component.

[0042] The red light LR, separated by dichroic mirror 121, shines on polarizer 105R through lens 143. The green light LG, separated by dichroic mirror 121, shines on polarizer 105G through lens 144. The blue light LB, separated by dichroic mirror 120, is reflected by mirror 131 and shines on polarizer 105B through lens 145.

[0043] Polarizing plates 105R, 105G, and 105B have the property of reflecting either s-polarized light or p-polarized light while allowing the other to pass through. For example, polarizing plates 105R, 105G, and 105B reflect s-polarized light while allowing p-polarized light to pass through. Polarizing plates 105R, 105G, and 105B are also called reflective polarizing plates.

[0044] Red light LR, which is p-polarized light, passes through polarizer 105R and illuminates display element 106R. Green light LG, which is p-polarized light, passes through polarizer 105G and illuminates display element 106G. Blue light LB, which is p-polarized light, passes through polarizer 105B and illuminates display element 106B.

[0045] Display elements 106R, 106G, and 106B are, for example, reflective liquid crystal display elements. In the following description, the case where display elements 106R, 106G, and 106B are reflective liquid crystal display elements will be used as examples, but the description is not limited to reflective types; a transmissive liquid crystal display element may also be used. Furthermore, this method can be widely applied to structures that use other display elements instead of liquid crystal display elements.

[0046] Display element 106R is controlled by image signal processing circuit 160. Image signal processing circuit 160 drives display element 106R based on image data of the red component. Display element 106R, under the control of image signal processing circuit 160, modulates the p-polarized red light LR to generate s-polarized red light LR. Display element 106G is controlled by image signal processing circuit 160. Image signal processing circuit 160 drives display element 106G based on image data of the green component. Display element 106G, under the control of image signal processing circuit 160, modulates the p-polarized green light LG to generate s-polarized green light LG. Display element 106B is controlled by image signal processing circuit 160. Image signal processing circuit 160 drives display element 106B based on image data of the blue component. Display element 106B, under the control of image signal processing circuit 160, modulates the p-polarized blue light LB based on image data of the blue component to generate s-polarized blue light LB.

[0047] Polarizing plates 107R, 107G, and 107B have the property of allowing either s-polarized light or p-polarized light to pass through, while reflecting or absorbing the other. For example, polarizing plates 107R, 107G, and 107B allow s-polarized light to pass through and absorb unwanted p-polarized light.

[0048] The red light LR of the s-polarized light generated by display element 106R is reflected by polarizer 105R, passes through polarizer 107R, and illuminates color combining prism 108. The green light LG of the s-polarized light generated by display element 106G is reflected by polarizer 105G, passes through polarizer 107G, and illuminates color combining prism 108. The blue light LB of the s-polarized light generated by display element 106B is reflected by polarizer 105B, passes through polarizer 107B, and illuminates color combining prism 108.

[0049] The color combining prism 108 combines the incident red light LR, green light LG, and blue light LB, and uses the resulting light L for image display to illuminate the projection lens 109. The light L is then projected through the projection lens 109 onto a screen (not shown) or similar object.

[0050] Furthermore, the irradiation device 100 has the structure described above, but its structure is not limited to the above description and can be any structure.

[0051] The optical path control device 10 includes an optical path control mechanism 12, a control circuit (control unit) 14, and a drive circuit (drive unit) 16. The optical path control mechanism 12 is a mechanism that oscillates by being driven by the drive circuit 16. The optical path control mechanism 12 is disposed between the color combining prism 108 and the projection lens 109 along the direction of the optical path of light L. The optical path control mechanism 12 receives the incident light L from the color combining prism 108 and oscillates, thereby shifting the travel direction (optical path) of light L so that it is emitted toward the projection lens 109. In this way, the optical path control device 10 controls the optical path of light L to shift the optical path of light L. In addition, the position of the optical path control mechanism 12 is not limited to between the color combining prism 108 and the projection lens 109, and can be arbitrary.

[0052] [Functional Structure of Display Devices]

[0053] Figure 2 It is a block diagram that schematically represents the circuit structure of a display device.

[0054] like Figure 2As shown, the image signal processing circuit 160 controls display elements 106R, 106B, and 106G. An image signal is input to the image signal processing circuit 160, which includes image data and a synchronization signal for controlling the display elements 106R, 106B, and 106G. The image signal processing circuit 160 synchronizes timing based on the synchronization signal and controls the display elements 106R, 106B, and 106G based on the image data. The control circuit 14 has a digital circuit 14A and a converter 14B. The synchronization signal from the image signal processing circuit 160 is input to the digital circuit 14A. The digital circuit 14A synchronizes timing based on the synchronization signal and generates a digital drive signal for driving the optical path control mechanism 12. The converter 14B is a DA converter that converts digital signals to analog signals. The converter 14B converts the digital drive signal generated by the digital circuit 14A into an analog drive signal. The drive circuit 16 receives an analog drive signal from the converter 14B, amplifies the analog drive signal, and outputs it to the actuator 12B of the optical path control mechanism 12 (described later). The actuator 12B is driven according to the drive signal, causing the swinging part 12A (described later, see reference 12B) to... Figure 3 )swing.

[0055] [Optical path control mechanism]

[0056] Figure 3 This is a top view showing the optical path control mechanism. Figure 4 yes Figure 3 Section IV-IV Figure 5 yes Figure 3 VV cross-sectional diagram.

[0057] like Figures 3 to 5 As shown, the optical path control mechanism 12 includes: a swinging part 12A, which includes an optical component (optical part) 20 into which light L is incident; and an actuator 12B, which causes the swinging part 12A to swing.

[0058] Actuator 12B causes the oscillating portion 12A to oscillate relative to the direction in which light L is incident on the optical component 20, centered on a first oscillating axis AX and a second oscillating axis BX that are intersecting (preferably orthogonal). The first oscillating axis AX and the second oscillating axis BX are preferably orthogonal. Therefore, the optical path control mechanism 12 has: a first oscillating portion 21 and a second oscillating portion 22 as the oscillating portion 12A; a first shaft portion 23 and a second shaft portion 24 along the first oscillating axis AX and the second oscillating axis BX; a first actuator 25 and a second actuator 26 as the actuator 12B; and a support portion 27.

[0059] Optical component 20 is a component that allows incident light L to pass through. Light L enters from one surface of optical component 20, through which it passes, and exits from its other surface. Optical component 20 is a glass plate, but the material and shape can be arbitrary.

[0060] The first swinging part 21 has an optical component 20 and a first movable part 31. The first movable part 31 is a component that supports the optical component 20. The first movable part 31 is fixed relative to the optical component 20. Specifically, the first movable part 31 is a frame-shaped component formed of a plate with a through hole 31a formed in the center. The optical component 20 is fixed to the first movable part 31 in a state of being inserted into the through hole 31a of the first movable part 31. In addition, the optical component 20 is fixed to the first movable part 31 via a fixing component for fixing to the first movable part 31 or an adhesive; however, the method of fixing the optical component 20 to the first movable part 31 can be arbitrary.

[0061] The second swing portion 22 is disposed outside the first swing portion 21. The second swing portion 22 has a second movable portion 32. The second movable portion 32 is a component that supports the first movable portion 31. The first movable portion 31 is supported on the second movable portion 32 so as to swing freely about the first swing axis AX. Specifically, the second movable portion 32 is a frame-shaped component formed of a plate with a through hole 32a formed in the center. The first movable portion 31 is disposed in the through hole 32a of the second movable portion 32 with a predetermined gap and is supported on the second movable portion 32 so as to swing freely. The first movable portion 31 and the second movable portion 32 are connected by a pair of first shaft portions 23 along the first swing axis AX. The first movable portion 31 elastically deforms in a manner that the pair of first shaft portions 23 twist relative to the second movable portion 32, thereby swinging about the first swing axis AX.

[0062] Support portion 27 is disposed outside the second swing portion 22. Support portion 27 is a component that supports the second movable portion 32. The second movable portion 32 is supported on support portion 27 so that it can swing freely about the second swing axis BX. Specifically, support portion 27 is a frame-shaped component formed of a plate with a through hole 27a formed in the center. The second movable portion 32 is disposed in the through hole 27a of support portion 27 with a predetermined gap and is supported on support portion 27 so that it can swing freely. The second movable portion 32 and support portion 27 are connected by a pair of second shaft portions 24 along the second swing axis BX. The second movable portion 32 elastically deforms in a manner that the pair of second shaft portions 24 twist relative to support portion 27, thereby swinging about the second swing axis BX.

[0063] The second movable part 32 (second swing part 22) swings relative to the support part 27 with a pair of second shafts 24 as fulcrums and with the second swing axis BX as the center. The first movable part 31 (first swing part 21) swings relative to the second movable part 32 with a pair of first shafts 23 as fulcrums and with the first swing axis AX as the center. Therefore, the optical component 20 fixed to the second movable part 32 can swing around the first swing axis AX and the second swing axis BX. By swinging the optical component 20 around the first swing axis AX and the second swing axis BX, the light path of the light L transmitted through the optical component 20 can be shifted by changing the posture of the optical component 20.

[0064] In the first embodiment, the first movable part 31, the second movable part 32, the first shaft part 23, and the second shaft part 24 are formed as a single unit. Therefore, the first movable part 31 can elastically deform by causing the first shaft part 23 to twist in the circumferential direction, thereby swinging relative to the second movable part 32. However, the first movable part 31, the second movable part 32, and the first shaft part 23 can also be formed separately and connected. Furthermore, one end and the other end of the axial direction of the second swing shaft BX in the second movable part 32 are fixed by connecting it to the support part 27, and a second shaft part 24 is formed at each end of the second movable part 32. However, a second shaft part 24 can also be provided at each end of the second movable part 32, and each second shaft part 24 can be fixed by directly connecting it to the support part 27. Alternatively, the second movable part 32, the second shaft part 24, and the support part 27 can be formed as a single unit.

[0065] The first actuator 25 causes the first movable part 31 (first swinging part 21) to swing relative to the support part 27 with a pair of first shaft parts 23 as fulcrums and with the first swinging axis AX as the center. The first actuator 25 is disposed on both sides of the first swinging axis AX, which are radially (axially) outside the second swinging axis BX. The first actuator 25 has a coil 41, a magnetic yoke 42, and a magnet 43.

[0066] Coils 41 are mounted on the first movable part 31 and fixed to the coil mounting part 31b provided on the first movable part 31. Coils 41 are respectively disposed at both ends radially of the first swing axis AX of the first movable part 31 (on one side and the other side axially of the second swing axis BX). A yoke 42 is a component forming a magnetic circuit. The yoke 42 is mounted on and fixed to the support part 27. The yoke 42 and coils 41 are respectively disposed at both ends of the first movable part 31. Magnets 43 are permanent magnets. Magnets 43 are mounted on and fixed to the yoke 42. Magnets 43 are positioned adjacent to each coil 41.

[0067] From drive circuit 16 (reference) Figure 2 A drive signal is input to coil 41. Figure 5In the example shown, a magnet 43 is attached to one side of the U-shaped yoke 42, and an air gap is formed between the unattached face of the magnet 43 and the opposite U-shaped face of the yoke 42. A coil 41 is disposed within this air gap. When a drive signal is input to the coil 41, current flows through it, generating a force that causes the first movable part 31 (first swinging part 21) fixed to the coil 41 to swing. The coil 41 is a conductor situated within the air gap (magnetic field) formed by the magnet 43 and the yoke 42. In other words, the first actuator 25 can be described as an electromagnetic actuator composed of the coil 41, the yoke 42, and the magnet 43.

[0068] The second actuator 26 causes the second movable part 32 (second swing part 22) to swing relative to the support part 27 with a pair of second shafts 24 as fulcrums and with the second swing axis BX as the center. The second actuator 26 is disposed on both one side and the other side that are radially (axially) outside the second swing axis BX. The second actuator 26 has a coil 44, a yoke 45 and a magnet 46.

[0069] Coils 44 are mounted on the second movable part 32 and fixed to the coil mounting part 32b provided on the second movable part 32. Coils 44 are respectively disposed at both ends radially of the second swing shaft BX of the second movable part 32 (on one side and the other side axially of the first swing shaft AX). A yoke 45 is a component forming a magnetic circuit. A yoke 45 is mounted on and fixed to the support part 27. The yoke 45 and coils 44 are respectively disposed at both ends of the second movable part 32. Magnets 46 are permanent magnets. Magnets 46 are mounted on and fixed to the yoke 45. Magnets 46 are positioned adjacent to each coil 44.

[0070] From drive circuit 16 (reference) Figure 2 A drive signal is input to coil 44. Figure 4 In the example shown, a magnet 46 is attached to one side of the U-shaped yoke 45, and an air gap is formed between the unattached face of the magnet 46 and the opposite U-shaped face of the yoke 45. A coil 44 is disposed within this air gap. When a drive signal is input to the coil 44, a current flows through it, generating a force that causes the second movable part 32 (second swinging part 22) fixed to the coil 44 to swing. The coil 44 is a conductor situated within the air gap (magnetic field) formed by the magnet 46 and the yoke 45. In other words, the second actuator 26 can be described as an electromagnetic actuator composed of the coil 44, the yoke 45, and the magnet 46.

[0071] In the optical path control mechanism 12, the first movable part 31 of the optical component 20 is provided to swing, and the second movable part 32 supporting the first movable part 31 swings. Therefore, it can be said that the optical component 20, the first movable part 31, the second movable part 32, and the coils 41 and 44 constitute the swing part 12A. That is, it can be said that the part of the optical path control mechanism 12 that swings relative to the support part 27 is the swing part 12A. In addition, the first shaft part 23 also swings together with the second movable part 32, and is therefore included in the swing part 12A. Furthermore, when a fixing member for fixing the optical component 20 to the first movable part 31, an adhesive, a substrate for allowing current to flow through the coils 41 and 44, leads, etc. are provided, these components also swing relative to the support part 27, and are therefore included in the swing part 12A.

[0072] In the first embodiment, the first movable part 31 is oscillated by the first actuator 25, and the second movable part 32 is oscillated by the second actuator 26. In this case, the magnetic yokes 42 and 45 constituting each actuator 25 and 26 are fixed to the support part 27. Therefore, when the second movable part 32 is oscillated by the second actuator 26, a gap is ensured between the first actuator 25 and the second movable part 32 to prevent interference. Alternatively, the first actuator 25 may be disposed on the second movable part 32.

[0073] Furthermore, actuators 25 and 26 are of the so-called moving-coil type, with coils 41 and 44 arranged in the movable portions 31 and 32, but are not limited to this. For example, they can also be of the so-called moving-magnet type, with magnets 43 and 46 arranged in the movable portions 31 and 32 and coils 41 and 44 arranged in the support portion 27. In this case, magnets 43 and 46 oscillate together with the optical component 20, and therefore, instead of coils 41 and 44, magnets 43 and 46 are included in the oscillating portion 12A.

[0074] The optical path control mechanism 12 has the structure described above, but is not limited to it. It can also be any structure in which the optical unit is oscillated by an actuator that is given a drive signal, thereby enabling the optical unit to shift the optical path of the light L.

[0075] [First shaft section and second shaft section]

[0076] Figure 6 This is a three-dimensional diagram showing the swinging part in the optical path control mechanism.

[0077] like Figure 6As shown, the first movable part 31 constituting the first swinging part 21 and the second movable part 32 constituting the second swinging part 22 are connected by a first shaft 23 along the first swinging axis AX, and the second movable part 32 and the support part 27 are connected by a second shaft 24 along the second swinging axis BX. Here, the mass of the first swinging part 21 and the distance from the first swinging axis AX to the outer periphery of the first movable part 31 are different from the mass of the second swinging part 22 and the distance from the second swinging axis BX to the outer periphery of the second swinging part 32. Therefore, the inertial torque when the first movable part 31 swings about the first shaft 23 by the first actuator 25 is different from the inertial torque when the second movable part 32 swings about the second shaft 24 by the second actuator 26.

[0078] That is, the inertial torque I1 of the first movable part 31 when the first movable part 31 is oscillating about the first swing axis AX with the first shaft part 23 as the fulcrum can be considered as follows. If the first movable part 31 is defined as an aggregate of particles with mass m1, and the distance of the particles from the first swing axis AX (the rotation radius of the particles) is defined as r1, then the inertial torque of the rotating particles is expressed by the following formula.

[0079] I1=m1·r1 2

[0080] The first movable part 31 is considered to be an assembly of point masses. Therefore, the inertial torque I of the first movable part 31 associated with the first swing axis AX is represented by the sum of the product of the mass m1, which is a small part of the first movable part 31, and the square of the distance from the first swing axis AX (rotation radius r1).

[0081] Similarly, the inertial torque I2 of the second movable part 32 when it oscillates around the second swing axis BX with the second shaft 24 as the fulcrum is caused by the second actuator 26 is represented by the sum of the product of the mass m2 of the small part of the second movable part 32 as a point mass and the square of the distance from the second swing axis BX (rotation radius r2). Therefore, the inertial torque of the first movable part 31 when it oscillates around the first swing axis AX is different from the inertial torque of the second movable part 32 when it oscillates around the second swing axis BX.

[0082] Therefore, the natural frequency of the first movable part 31 when it swings is different from the natural frequency of the second movable part 32 when it swings, and their displacement times are different. In the display device 1, sometimes an image is displayed while the optical component 20 is swinging. If the displacement time of the first movable part 31 is different from the displacement time of the second movable part 32, the visual perception of the image output during their respective swings will be different, and the image quality will be reduced.

[0083] In the first embodiment, the torsional stiffness of the second shaft portion 24 is set to be higher than that of the first shaft portion 23. This is achieved by making at least one of the cross-sectional area, length, and material different between the first shaft portion 23 and the second shaft portion 24, thereby making the torsional stiffness of the second shaft portion 24 higher than that of the first shaft portion 23.

[0084] The natural frequencies of the first movable part 31 and the second movable part 32 are determined by the inertial torque about the axis and the torsional stiffness of the axis. The inertial torque about the axis is determined by the mass of the first swing part 21 and the mass of the second swing part 22, the distance from the first swing axis AX to the first movable part 31, and the distance from the second swing axis BX to the second swing part 32. On the other hand, the torsional stiffness of the axis is determined by the cross-sectional area, length, and material of the first shaft part 23 and the second shaft part 24. The distance from the second swing axis BX to the second swing part 32 is longer than the distance from the first swing axis AX to the first movable part 31, therefore the inertial torque of the second movable part 32 is greater than that of the first movable part 31, and its natural frequency is lower. Therefore, by making the torsional stiffness of the second shaft part 24 higher than that of the first shaft part 23, the inertial torque of the second movable part 32 is reduced, and its natural frequency is increased. Thus, the natural frequency of the first movable part 31 is approximately the same as that of the second movable part 32, preferably equal.

[0085] Once the natural frequency of the first movable part 31 and the natural frequency of the second movable part 32 become the same, the displacement time of the first movable part 31 and the displacement time of the second movable part 32 become the same, thereby making the visual perception of the image output during their respective swings the same and suppressing the degradation of image quality.

[0086] In the first embodiment, the first shaft portion 23 and the second shaft portion 24 are made of the same material. The radial lengths L1 and L2 of the first shaft portion 23 and the second shaft portion 24 are the same. The cross-sectional areas of the first shaft portion 23 and the second shaft portion 24 are different. The cross-sectional area of ​​the first shaft portion 23 is width W1 × thickness T1, and the cross-sectional area of ​​the second shaft portion 24 is width W2 × thickness T2. Furthermore, since torsional stiffness is proportional to cross-sectional area, the cross-sectional area (width W1 × thickness T1) of the first shaft portion 23 is set to be less than the cross-sectional area (width W2 × thickness T2) of the second shaft portion 24. Additionally, since torsional stiffness is inversely proportional to axial length, the length L1 of the first shaft portion 23 can also be greater than the length L2 of the second shaft portion 24. By making at least one of the cross-sectional area, length, and material different between the first shaft portion 23 and the second shaft portion 24, the torsional stiffness of the second shaft portion 24 is made higher than that of the first shaft portion 23. For example, when the thicknesses T1 and T2 of the first shaft portion 23 and the second shaft portion 24 are the same and the axial lengths L1 and L2 of the first shaft portion 23 and the second shaft portion 24 are the same, by making the width W2 of the second shaft portion 24 greater than the width W1 of the first shaft portion 23, the torsional stiffness of the second shaft portion can be made to be greater than that of the first shaft portion in different ways.

[0087] [Drive Signal]

[0088] Here, the drive signal applied from the drive circuit 16 to the actuator 12B will be explained. Figure 7 It is a graph illustrating the waveform of the drive signal of the drive unit.

[0089] like Figure 7 As shown, the drive signal applied from the drive circuit 16 to the first actuator 25 is an electrical signal, and the current value changes over time. Hereinafter, the waveform representing the change in current value of the drive signal over time will be referred to as the waveform of the drive signal. The waveform of the drive signal is... Figure 7 The solid lines represent the driving signal. The same waveform is repeated in each period T. Period T includes period T1 and period T2, which follows and is continuous with period T1. Period T1 corresponds to the period of the image (image without offset by half a pixel) when the optical axis of the display light L is in the first position, and period T2 corresponds to the period of the image (image offset by half a pixel) when the optical axis of the display light L is in the second position.

[0090] During the first period TA1 of period T1, the current value of the drive signal changes from a first current value A1 to a second current value A2. Here, the midpoint between the first current value A1 and the second current value A2, 0, is the position where the current value is 0. During the first period TA1, the current value changes linearly from the first current value A1 to the second current value A2 over time. That is, at the beginning of the first period TA1, the current value is the first current value A1, then the current value changes linearly from the first current value A1, and at the end of the first period TA1, the current value is the second current value A2. The first current value A1 is the current value that can maintain the first swinging part 21 at a first angle D1, and is set according to the value of the first angle D1. The second current value A2 is the current value that can maintain the first swinging part 21 at a second angle D2, and is set according to the value of the second angle D2. The first current value A1 and the second current value A2 are current values ​​with opposite signs, and their absolute values ​​can be equal. Figure 7 The example illustrates the case where the first current value A1 is negative and the second current value A2 is positive.

[0091] The length of the first period TA1 is a value corresponding to the natural frequency of the first oscillating part 21. The first oscillating part 21 refers to the portion of the optical path control mechanism 12 that oscillates relative to the support part 27 (in the first embodiment, this is the optical component 20, the first movable part 31, and the coil 41). That is, the length of the first period TA1 can be said to be a value corresponding to the natural frequency of the portion that oscillates relative to the support part 27. More specifically, the length of the first period TA1 is preferably a value that is approximately the same as the natural period of the first oscillating part 21, and more preferably a value that is the same as the natural period. Here, the natural period is the reciprocal of the natural frequency. In addition, "approximately the same value" means a value that allows for a deviation from the error range relative to the natural period. For example, if the deviation relative to the natural period is within 5% of the value of the natural period, it can also be set to "approximately the same value". Hereinafter, the description of "approximately the same value" also means the same thing. Furthermore, when the natural frequency is set to f [Hz], the value of the natural period (the reciprocal of the natural frequency) is expressed as "1 / f" [s].

[0092] During the second period TB1 of period T1, the current value of the drive signal is maintained at the second current value A2. The second period TB1 is a period following and continuous with the first period TA1. Furthermore, by increasing the inherent frequency of the first oscillating part 21, the first period TA1 can be shortened, and the second period TB1 can be lengthened (e.g., it can be made longer than the first period TA1), which is therefore preferred. Moreover, maintaining the current value at the second current value A2 is not limited to the current value strictly remaining unchanged from the second current value A2; it can also include cases where the current value deviates from the second current value A2 within a predetermined range. This predetermined value can be arbitrarily set, for example, it can be a value of 10% of the second current value A2.

[0093] In this way, the current value of the drive signal gradually changes from the first current value A1 to the second current value A2 during the period T1. If the current value reaches the second current value A2, the current value is maintained at the second current value A2.

[0094] During the third period TA2 within period T2, the current value of the drive signal changes from the second current value A2 to the first current value A1. The third period TA2 can be considered as the period following and continuing from the second period TB1. More specifically, during the third period TA2, the current value of the drive signal changes linearly from the second current value A2 to the first current value A1 over time. That is, at the beginning of the third period TA2, the current value is the second current value A2, then changes linearly from the second current value A2, and at the end of the third period TA2, the current value becomes the first current value A1.

[0095] The length of the third period TA2 is a value corresponding to the natural frequency of the first oscillating part 21. More specifically, the length of the third period TA2 is preferably approximately the same as the natural period (the reciprocal of the natural frequency) of the first oscillating part 21, and more preferably the same as the natural period. In the third period TA2, the length of the third period TA2 is equal to the length of the first period TA1.

[0096] During the fourth period TB2 of period T2, the current value of the drive signal is maintained at the first current value A1. The fourth period TB2 is a period following and continuous with the third period TA2. Additionally, the fourth period TB2 is a period preceding and continuous with the first period TA1. The fourth period TB2 is equal to the second period TB1. Increasing the inherent frequency of the first oscillating section 21 can shorten the third period TA2 and lengthen the fourth period TB2 (e.g., make it longer than the third period TA2), which is therefore preferred. Furthermore, maintaining the current value at the first current value A1 is not limited to the current value strictly remaining unchanged from the first current value A1; it can also include cases where the current value deviates from the first current value A1 within a predetermined range. This predetermined value can be arbitrarily set, for example, it can be a value of 10% of the first current value A1.

[0097] In this way, the current value of the drive signal gradually changes from the second current value A2 to the first current value A1 during the period T2. If the current value reaches the first current value A1, the current value is maintained at the first current value A1.

[0098] As described above, in the first embodiment, the waveform of the drive signal is trapezoidal, and the first period TA1 and the third period TA2 during which the current value changes become values ​​corresponding to the inherent frequency of the swing section 12A.

[0099] in addition, Figure 7 The dashed lines indicate the periods of illumination L. The illumination device 100 preferably does not illuminate L during the first period TA1, but illuminates L during the second period TB1. Furthermore, the illumination device 100 preferably does not illuminate L during the third period TA2, but illuminates L during the fourth period TB2.

[0100] [Swing Mode]

[0101] Next, the swing mode of the first swing unit 21 based on the application of the drive signal will be described. Figure 8 It is a graph illustrating the single-axis oscillation mode of the optical section.

[0102] like Figure 8 As shown, the oscillation pattern of the first oscillating part 21 refers to the displacement angle (angle about the first oscillation axis AX) of the first oscillating part 21 at each time interval when a drive signal is applied to the first actuator 25. Figure 8 In the middle, the oscillation pattern is represented by a solid line.

[0103] During the first period TA1, the current value of the drive signal changes from a first current value A1 to a second current value A2. Consequently, the displacement angle of the first swing unit 21 changes from a first angle D1 to a second angle D2 during the first period TA1. Here, the midpoint O between the first angle D1 and the second angle D2 is the position where the displacement angle of the first swing unit 21 is 0.

[0104] During the second period TB1, the current value of the drive signal is maintained at the second current value A2. Therefore, during the second period TB1, the displacement angle of the first swing unit 21 is maintained at the second angle D2. Furthermore, maintaining it at the second angle D2 is not limited to the displacement angle remaining strictly unchanged from the second angle D2; it can also include cases where the displacement angle deviates from the second angle D2 within a predetermined range. This predetermined value can be arbitrarily set, for example, it could be 10% of the second angle D2.

[0105] During the third period TA2, the current value of the drive signal changes from the second current value A2 to the first current value A1. As a result, the displacement angle of the first swinging part 21 changes from the second angle D2 to the first angle D1 during the third period TA2.

[0106] During the fourth period TB2, the current value of the drive signal is maintained at the first current value A1. Therefore, the displacement angle of the first swing unit 21 is maintained at the first angle D1 during the fourth period TB2. Furthermore, maintaining it at the first angle D1 is not limited to the displacement angle remaining strictly unchanged from the first angle D1; it can also include cases where the displacement angle deviates from the first angle D1 within a predetermined range. This predetermined value can be arbitrarily set, for example, it could be 10% of the first angle D1.

[0107] Furthermore, light L is illuminated during the second period TB1 and the fourth period TB2. Therefore, during the second period TB1, light L is illuminated onto the first swing portion 21 held at the second angle D2, and the optical path of light L becomes the first position. During the fourth period TB2, light L is illuminated onto the first swing portion 21 held at the first angle D1, and the optical path of light L shifts to the second position, causing the image to shift by half a pixel.

[0108] In the optical path control device 10 that shifts the optical path by oscillating the optical component 20, it is required that the optical component 20 oscillates stably. In the first embodiment, by setting the lengths of the first period TA1 and the third period TA2 to values ​​corresponding to the natural frequency of the first oscillating part 21, vibration of the first oscillating part 21 can be suppressed in the second period TB1 and the fourth period TB2, thereby making the first oscillating part 21 oscillate stably. That is, by making the lengths of the first period TA1 and the third period TA2 to values ​​corresponding to the natural frequency of the first oscillating part 21, vibration of the first oscillating part 21 in the second period TB1 and the fourth period TB2 can be suppressed, thereby making the first oscillating part 21 oscillate stably. Therefore, the first oscillating part 21 can oscillate at high speed and remain stably stationary, suppressing image degradation.

[0109] Here, the drive signal applied to the first actuator 25, which is the drive signal applied from the drive circuit 16 to the actuator 12B, is described. Similarly, the drive signal applied to the second actuator 26 is also described, so the description is omitted.

[0110] [Pixel movement based on optical path control mechanism]

[0111] The following describes the operation of the first swinging part 21 and the second swinging part 22 when they swing. Figure 9 This is an explanatory diagram illustrating the dual-axis oscillation mode of the optical section.

[0112] In the optical path control mechanism 12 of the first embodiment, the first actuator 25 and the second actuator 26 constituting the actuator 12B respectively cause the first swing portion 21 and the second swing portion 22 to swing according to the drive signal, so as to repeatedly perform posture changes from the first angle D1 to the second angle D2 and from the second angle D2 to the first angle D1 around the first axis portion AX and the second axis portion BX. By repeatedly swinging between the first angle D1 and the second angle D2 by the first swing portion 21 and the second swing portion 22 respectively, the optical axis of the light L repeatedly shifts from the first position to the second position and from the second position to the first position.

[0113] That is, the image projected onto the screen by light L when the optical axis is at the first position is offset by half a pixel from the image projected onto the screen when the optical axis is at the second position. In other words, the image projected onto the screen is repeatedly offset by half a pixel and then returns to its original position. This increases the apparent number of pixels, enabling a higher resolution image projected onto the screen. Since the optical axis shift is half a pixel, the first angle D1 and the second angle D2 are set to angles capable of shifting the image by half a pixel. Furthermore, the image shift is not limited to half a pixel; it can be any amount, such as 1 / 4 or 1 / 8 of a pixel. The first angle D1 and the second angle D2 can also be appropriately set according to the image offset.

[0114] The following is a detailed explanation. Here, the first swing axis AX direction and the second swing axis BX direction intersect orthogonally, parallel to the pixel arrangement direction. For example... Figure 3 as well as Figure 9As shown, image position P0 is the display position when the current values ​​applied to the first actuator 25 and the second actuator 26 are set to 0, that is, when the displacement angle of the optical component 20 is 0. Operation state A is as follows: the first actuator 25 causes the optical component 20 to swing around the first swing axis AX by a predetermined angle, shifting image position P0 by 1 / 4 pixel towards the second swing axis BX; and the second actuator 26 causes the optical component 20 to swing around the second swing axis BX by a predetermined angle, shifting image position P0 by 1 / 4 pixel towards the first swing axis AX. That is, operation state A is the state where the image is displayed at image position P1, where image position P1 is the position where image position P0 is shifted towards a direction ABXa, which is the resultant of the vectors in one direction towards the first swing axis AX and the vectors in one direction towards the second swing axis BX.

[0115] Similarly, action state B is the state where the image is displayed at image position P2. Image position P2 is the position offset from image position P0 towards the direction ABXb, which is the result of combining a vector pointing towards the first swing axis AX and a vector pointing towards the second swing axis BX. Similarly, action state C is the state where the image is displayed at image position P3. Image position P3 is the position offset from image position P0 towards the direction ABXc, which is the result of combining a vector pointing towards the first swing axis AX and a vector pointing towards the second swing axis BX. Similarly, action state D is the state where the image is displayed at image position P4. Image position P4 is the position offset from image position P0 towards the direction ABXd, which is the result of combining a vector pointing towards the first swing axis AX and a vector pointing towards the second swing axis BX.

[0116] The swing patterns of the first swinging part 21 and the second swinging part 22 in the above-mentioned pixel operation state will be described. Figure 10 It is a graph illustrating the biaxial oscillation mode when the natural frequencies of the first and second shafts are different. Figure 11 It is a graph illustrating the biaxial oscillation mode when the natural frequencies of the first and second shafts are the same.

[0117] In the following description, the oscillation pattern of the first oscillating part 21 refers to the displacement angle (angle about the first oscillation axis AX) of the first oscillating part 21 at each time when a drive signal is applied to the first actuator 25, and is represented by a solid line. Conversely, the oscillation pattern of the second oscillating part 22 refers to the displacement angle (angle about the second oscillation axis BX) of the second oscillating part 22 at each time when a drive signal is applied to the second actuator 26, and is represented by a dashed line.

[0118] like Figure 10As shown, during the displacement period TA2-A, the current value of the drive signal changes from the second current value A2 to the first current value A1 (refer to...). Figure 7 Therefore, during the displacement period TA2-A, the displacement angle of the first swinging part 21 changes from the second angle D2 to the first angle D1. During the displacement period TA2-B, the current value of the drive signal changes from the second current value A2 to the first current value A1. Therefore, during the displacement period TA2-B, the displacement angle of the second swinging part 22 changes from the second angle D2 to the first angle D1.

[0119] Furthermore, during the displacement period TA1-C, the current value of the drive signal changes from the first current value A1 to the second current value A2. Consequently, during the displacement period TA1-C, the displacement angle of the first swing unit 21 changes from the first angle D1 to the second angle D2. During the displacement period TA1-D, the current value of the drive signal changes from the first current value A1 to the second current value A2. Consequently, during the displacement period TA1-D, the displacement angle of the second swing unit 22 changes from the first angle D1 to the second angle D2.

[0120] During displacement periods TA2-A, TA2-B, TA1-C, and TA1-D, respectively, they represent the displacements to... Figure 9 The transition periods between operation states A, B, C, and D are described in the text. When the inherent frequencies of the first axis 23 and the second axis 24 are different, for example, because the lengths of the displacement period TA2-A and TA2-B are different, the lengths of the display period TB2-A and TB2-B during current maintenance are also different. This results in different visual perceptions of the image in operation states A and B, and a decrease in image quality. The same applies to operation states C and D. On the other hand, as... Figure 11 As shown, when the inherent frequencies of the first shaft portion 23 and the second shaft portion 24 are the same, since the lengths of the displacement period TA2-A and the displacement period TA2-B are the same, the lengths of the display period TB2-A and the display period TB2-B when maintaining the current are the same. Therefore, the visual perception of the image is the same in both the A operation state and the B operation state, and the degradation of image quality can be suppressed.

[0121] In the first embodiment, when the optical component 20 is made to oscillate along two axes, the torsional stiffness of the second axis portion 24 is higher than that of the first axis portion 23. The second axis portion 24 is the center of the oscillation axis that has a larger moment of inertia of the optical component 20, and the first axis portion 23 is the center of the oscillation axis that has a smaller moment of inertia of the optical component 20. As a result, the natural frequency of the first oscillation portion 21 is approximately the same as that of the second oscillation portion 22, and the lengths of the displacement periods TA1-C and TA2-A of the first oscillation portion 21 are the same as the lengths of the displacement periods TA1-D and TA2-B of the second oscillation portion 22, which can suppress image degradation.

[0122] As described above, in the optical path control mechanism 12 that causes the optical component 20 to swing twice, the lengths of the displacement periods TA1-C and TA2-A of the first swing portion 21 are the same as the lengths of the displacement periods TA1-D and TA2-B of the second swing portion 22, thus suppressing image degradation. In this case, the natural frequency of the first swing portion 21 is the same as the natural frequency of the second swing portion 22. The displacement time is proportional to the natural frequency of each swing portion 21, 22; if the natural frequency increases, the displacement time decreases (displacement speed increases), and if the natural frequency decreases, the displacement time increases (displacement speed decreases). Furthermore, when the natural frequency of the first swing portion 21 and the natural frequency of the second swing portion 22 overlap with an integer multiple (odd number) of the frame rate, each swing portion 21, 22 generates unwanted vibrations caused by resonance, making it impossible to keep the optical component 20 stably stationary.

[0123] Therefore, in the optical path control device 10 of the first embodiment, the inherent frequency of the first swinging part 21 and the inherent frequency of the second swinging part 22 are set to values ​​offset from odd multiples of the corresponding frame rates.

[0124] Specifically, the natural frequency of the first swinging part 21 and the natural frequency of the second swinging part 22 are set to values ​​that are larger than an odd number (n) times the corresponding frame rate and smaller than an odd number (n+2) times the corresponding frame rate.

[0125] The optical path control mechanism 12 applies a trapezoidal waveform (trapezoidal wave) drive signal to the first actuator 25 and the second actuator 26 via the drive circuit 16, thereby causing the first swinging part 21 and the second swinging part 22 to swing. This trapezoidal wave can be represented by a sum of trigonometric functions through Fourier series expansion. As described below, the mathematical expression of these trigonometric functions can be represented by the fundamental wave and odd harmonics, and can become... Figure 7 The approximation of the trapezoidal wave is shown.

[0126] F(x)=(4 / π)×{sin(x)+(1 / 4)×sin(3x)+(1 / 10)×sin(5x)+(1 / 25)×sin(7x)}

[0127] Therefore, if the odd harmonic components overlap with the natural frequency, the vibration of the first oscillating part 21 and the second oscillating part 22 will increase. This has also been confirmed in actual operation and measurement.

[0128] The displacement time of the first swing portion 21 and the second swing portion 22 is proportional to their natural frequencies. When the natural frequencies of the first swing portion 21 and the second swing portion 22 overlap with an odd multiple of the frame rate, the first swing portion 21 and the second swing portion 22 generate unwanted vibrations caused by resonance, making it impossible to keep the optical component 20 stably stationary. Therefore, in the first embodiment, the natural frequencies of the first swing portion 21 and the second swing portion 22 are set as large as possible, making them frequencies offset from an odd multiple of the frame rate.

[0129] That is, the inherent frequencies of the first swinging part 21 and the second swinging part 22 are set between the same frame rate × n (odd number) and frame rate × (n+2), and all corresponding frame rates are satisfied.

[0130] Frame rate × n (odd number) < inherent frequency < frame rate × (n+2)

[0131] The display device 1 is configured with multiple frame rates. Therefore, it is preferable to set the inherent frequency of the first swinging part 21 and the inherent frequency of the second swinging part 22 to values ​​offset from odd multiple multiple frame rates.

[0132] For example, in cases corresponding to three frame rates of 60Hz, 50Hz, and 48Hz, the inherent frequencies of the first swing section 21 and the second swing section 22 are set to frequencies that satisfy the following three conditions.

[0133] 180Hz (60×3) < Natural frequency < 300Hz (60×5)

[0134] 250Hz (50×5) < natural frequency < 350Hz (50×7)

[0135] 240Hz (48×5) < Natural frequency < 336Hz (48×7)

[0136] That is, the natural frequencies of the first swinging part 21 and the second swinging part 22 are within the following range.

[0137] 250Hz < natural frequency < 300Hz

[0138] Thus, in the optical path control device 10 of the first embodiment, the natural frequencies of the first oscillating part 21 and the second oscillating part 22 are set to values ​​offset from odd multiples of the corresponding frame rates. Therefore, unwanted vibrations caused by the resonance of the first oscillating part 21 and the second oscillating part 22 can be suppressed, and the optical component 20 can be kept stably stationary.

[0139] <Second Implementation Method>

[0140] Figure 12 This is a cross-sectional view showing the optical path control mechanism according to the second embodiment. Figure 13 This is a block diagram schematically illustrating the circuit structure of the display device. It should be noted that components having the same functions as in the first embodiment described above are labeled with the same reference numerals, and detailed descriptions are omitted.

[0141] In the second embodiment, such as Figure 12 as well as Figure 13 As shown, it has an optical path control mechanism 12, a control circuit 14, and a drive circuit 16.

[0142] The optical path control mechanism 12 has a swing section 12A and an actuator 12B. The swing section 12A includes an optical component 20, and the actuator 12B causes the swing section 12A to swing. The swing section 12A has a first swing section 21 and a second swing section 22. The first swing section 21 swings relative to the second swing section 22 via a first shaft portion 23 along a first swing axis AX. The second swing section 22 swings relative to a support portion 27 via a second shaft portion 24 along a second swing axis BX. The actuator 12B has a first actuator 25 and a second actuator 26. The first actuator 25 causes the first swing section 21 to swing, and the second actuator 26 causes the second swing section 22 to swing.

[0143] The optical path control mechanism 12 is driven by the drive circuit 16 to drive the first actuator 25 and the second actuator 26, thereby causing the first swing part 21 and the second swing part 22 to swing. The drive circuit 16 applies a trapezoidal wave drive signal to the first actuator 25 and the second actuator 26, thereby causing the first swing part 21 and the second swing part 22 to swing.

[0144] As described in the first embodiment, the inherent frequencies of the first swing portion 21 and the second swing portion 22 are set to predetermined values. Based on the inherent frequencies of the first swing portion 21 and the second swing portion 22, the optical path control device 10 sets the length of each displacement period, and sets the trapezoidal wave of the drive signal in such a way that the current value changes during the displacement period of the predetermined length.

[0145] Furthermore, the parameters of the drive circuit 16, which includes the trapezoidal wave of the drive signal, are pre-adjusted before being mounted on the product. However, for example, due to installation deviations of the optical path control mechanism 12, optical path control device 10, etc., on the display device 1, changes over time, environmental changes, etc., the natural frequency of the vibrating part may change. In this case, it is difficult to readjust the trapezoidal wave of the drive signal.

[0146] Therefore, in the second embodiment, a vibration sensor is mounted on the optical path control device 10, and the trapezoidal wave of the drive signal is adjusted based on the frequencies of the first swing portion 21 and the second swing portion 22 detected by the vibration sensor. Furthermore, the waveform of the drive signal is not limited to a trapezoidal shape; it can also be a stepped shape, a rectangular shape, etc.

[0147] That is, in addition to the optical path control mechanism 12, control circuit 14, and drive circuit 16, the optical path control device 10 also has a vibration sensor 17 and a parameter setting unit 18.

[0148] Vibration sensor 17 is mounted on support 27. Vibration sensor 17 is capable of detecting the frequencies of the first swing part 21 and the second swing part 22, which are swing parts 12A. Parameter setting unit 18 adjusts and sets the trapezoidal wave of the drive signal applied by drive circuit 16 to the first actuator 25 and the second actuator 26 based on the frequencies of the first swing part 21 and the second swing part 22 detected by vibration sensor 17.

[0149] That is, a sine wave is applied (scanned) to the first actuator 25 by the drive circuit 16 while gradually increasing the frequency from 0Hz. At this time, the vibration sensor 17 disposed on the support 27 measures the vibration of the first swinging part 21. Furthermore, the parameter setting unit 18 sets the frequency at which the first swinging part 21 vibrates to its maximum (resonance) frequency as the natural frequency of the first swinging part 21 based on the vibration of the first swinging part 21 detected by the vibration sensor 17.

[0150] Similarly, a sine wave is applied (scanned) to the second actuator 26 by the drive circuit 16 while gradually increasing the frequency from 0Hz. At this time, the vibration sensor 17 disposed on the support 27 measures the vibration of the second swing section 22. Furthermore, the parameter setting unit 18 sets the frequency at which the second swing section 22 vibrates at its maximum (resonance) as the natural frequency of the second swing section 22 based on the vibration of the second swing section 22 detected by the vibration sensor 17.

[0151] The control circuit 14 sets the trapezoidal wave of the drive signal, i.e., the length of the displacement period, based on the inherent frequencies of each swing unit 21 and 22 set by the parameter setting unit 18. Furthermore, the control circuit 14 sets the trapezoidal wave of the drive signal in such a way that the current value changes during the displacement period of the set length.

[0152] Thus, in the optical path control device 10 of the second embodiment, a vibration sensor 17 is mounted on the optical path control device 10. The vibration sensor 17 detects the natural frequencies of the first swinging part 21 and the second swinging part 22. The parameter setting unit 18 adjusts and sets the waveform of the drive signal based on the frequencies of the first swinging part 21 and the second swinging part 22 detected by the vibration sensor 17. Therefore, even if the natural frequency of the vibrating part changes due to installation deviations of the optical path control mechanism 12, the optical path control device 10, etc., to the display device 1, changes over time, environmental changes, etc., the drive waveform (trapezoidal wave) used to swing the first swinging part 21 and the second swinging part 22 can be easily adjusted when the display device 1 is manufactured. In addition, even if the natural frequency shifts due to aging of the constituent components after the display device 1 is manufactured, the drive waveform (trapezoidal wave) of the first swinging part 21 and the second swinging part 22 can be adjusted when needed.

[0153] (Effect)

[0154] As described above, the optical path control device according to this embodiment includes: a swinging part 12A, which has: an optical component (optical part) 20 for light incident; a first swinging part 21 for supporting the optical component 20; and a second swinging part 23, which is supported by a first shaft 23 and is supported by a second shaft 24 on a support part 27; a first actuator 25 for swinging the swinging part 12A about the first shaft 23 as a fulcrum and about a first swinging axis AX including the first shaft 23 as a center; and a second actuator 26 for swinging the swinging part 12A about the second shaft 24 as a fulcrum and about a second swinging axis BX including the second shaft 24 as a center, wherein the first swinging axis AX intersects the second swinging axis BX, and the torsional stiffness of the second shaft 24 is higher than that of the first shaft 23.

[0155] According to the optical path control device of this embodiment, by setting the torsional stiffness of the outer second shaft portion 24 to be higher than the torsional stiffness of the inner first shaft portion 23, the natural frequencies of the optical component 20 oscillating around the first shaft portion 23 and the optical component 20 oscillating around the second shaft portion 24 can be made close. Therefore, the visual perception of the image output when the optical component 20 oscillates based on the first shaft portion 23 is the same as that of the image output when the optical component 20 oscillates based on the second shaft portion 24, and the degradation of image quality can be suppressed.

[0156] Furthermore, the optical path control device according to this embodiment sets the torsional stiffness of the first shaft portion 23 and the torsional stiffness of the second shaft portion 24 such that the natural frequencies of the first swing portion 21 and the second swing portion 22 fall within a predetermined range. Therefore, by setting the displacement time of the first swing portion 21 and the second swing portion 22 to the same length, it is possible to suppress the degradation of image quality.

[0157] Furthermore, the optical path control device according to this embodiment differs in at least one of the cross-sectional area, length, and material between the first shaft portion 23 and the second shaft portion 24, thereby making the torsional stiffness of the second shaft portion 24 higher than that of the first shaft portion 23. Therefore, it is easy to make the natural frequency of the first swing portion 21 close to the natural frequency of the second swing portion 22.

[0158] As explained above, the optical path control device according to this embodiment may also include: a swinging part 12A having an optical component (optical part) 20 for light incident; an actuator 12B for swinging the swinging part 12A; a drive circuit 16 for controlling the optical path of light transmitted through the optical component 20 by applying a drive signal to the actuator 12B to swing the swinging part 12A, wherein the waveform of the drive signal includes a first period for changing the current value and a second period for maintaining the current value; a vibration sensor 17 for detecting the frequency of the swinging part 12A; and a parameter setting unit 18 for setting the drive signal of the waveform based on the frequency of the swinging part 12A detected by the vibration sensor 17.

[0159] According to the optical path control device of this embodiment, the vibration sensor 17 detects the frequency of the oscillating part 12A, and the parameter setting unit 18 sets the drive signal waveform based on the frequency of the oscillating part 12A. This allows for real-time adjustment of the deviation of the drive signal waveform corresponding to the mounting positions of the optical component 20, the oscillating part, the actuator 12B, and other constituent components. Therefore, the waveform of the drive signal used to drive the actuator 12B can be automatically adjusted, thereby reducing operating time.

[0160] Furthermore, in the optical path control device according to this embodiment, the oscillation unit 12A includes a first oscillation unit 21 that supports the optical component 20 and a second oscillation unit 22 that supports the first oscillation unit 21 freely. The second oscillation unit 22 is supported freely on the support unit 27, and the natural frequencies of the first oscillation unit 21 and the second oscillation unit 22 are set to fall within a predetermined range. Therefore, resonance (unwanted vibration) between the first oscillation unit 21 and the second oscillation unit 22 can be suppressed, allowing the optical component 20 to remain stably stationary.

[0161] Furthermore, the optical path control device according to this embodiment mounts a vibration sensor on the support 27. Therefore, the natural frequencies of the first swinging part 21 and the second swinging part 22 can be detected with high precision using the vibration sensor 17.

[0162] As explained above, the optical path control device according to this embodiment may also include: a first swinging part 21 supporting an optical component (optical part) 20 for light incidence; a second swinging part 22 supporting the first swinging part 21 by means of a first shaft part 23; a support part 27 supporting the second swinging part 22 by means of a second shaft part 24; a first actuator 25 causing the first swinging part 21 to swing about the first shaft part 23 as a fulcrum; and a second actuator 26 causing the second swinging part 22 to swing about the second shaft part 24 as a fulcrum, wherein the natural frequency of the first swinging part 21 and the natural frequency of the second swinging part 22 are set to be offset from an odd multiple of the corresponding frame rate.

[0163] According to the optical path control device of this embodiment, by setting the natural frequency of the first oscillating part 21 and the natural frequency of the second oscillating part 22 to values ​​offset from odd multiples of the frame rate, resonance (unwanted vibration) of the first oscillating part 21 and the second oscillating part 22 can be suppressed, and the optical component 20 can be stably kept still. Therefore, the visual perception of the image output when the optical component 20 based on the first axis 23 oscillates is the same as that of the image output when the optical component 20 based on the second axis 24 oscillates, and the degradation of image quality can be suppressed.

[0164] Furthermore, the optical path control device according to this embodiment sets the natural frequency of the first swing unit 21 and the natural frequency of the second swing unit 22 to values ​​that are larger than an odd number (n) times the corresponding frame rate and smaller than an odd number (n+2) times the corresponding frame rate. Therefore, the resonance (unwanted vibration) of the first swing unit 21 and the second swing unit 22 can be appropriately suppressed.

[0165] Furthermore, the optical path control device according to this embodiment makes the torsional stiffness of the second shaft portion 24 higher than that of the first shaft portion 23. Therefore, it is possible to make the natural frequencies of the optical component 20 that oscillates with the first shaft portion 23 as the fulcrum and the optical component 20 that oscillates with the second shaft portion 24 as the fulcrum close.

[0166] Furthermore, the optical path control device according to this embodiment sets the inherent frequency of the first oscillating part 21 and the inherent frequency of the second oscillating part 22 to values ​​offset from odd multiples of the corresponding multiple frame rates. Therefore, resonance of the first oscillating part 21 and the second oscillating part 22 can be suppressed relative to the multiple frame rates.

[0167] Furthermore, the display device according to this embodiment includes a light path control device 10 and an illumination device 100 for irradiating the swing portion 12A with light L. By including the light path control device 10, the display device 1 can stably swing the swing portion 12A and suppress image degradation.

[0168] Furthermore, in the above-described embodiment, the optical component 20 is configured to be supported by a first shaft portion 23 that can swing freely along the first swing axis AX, and the optical component 20 is supported by a second shaft portion 24 that can swing freely along the second swing axis BX, but is not limited to this configuration.

[0169] It can also be configured to support the optical component 20 by a single axis instead of a biaxial one, or it can be configured to support the optical component 20 by a biaxial three or more axes instead of a biaxial one.

[0170] This concludes the description of the optical path control device 10 involved in the present invention. However, it can be implemented in various other ways besides the embodiments described above.

[0171] The components of the optical path control device 10 shown in the figure are functional concepts and may not be physically configured as shown. That is, the specific configuration of each device is not limited to the configuration shown in the figure. Depending on the processing load, usage conditions, etc., all or part of each device may be functionally or physically distributed or integrated in any unit.

[0172] The optical path control device 10 is configured as software, for example, by a program loaded into memory. In the above embodiment, functional modules implemented through the cooperation of these hardware or software components have been described. That is, these functional modules can be implemented in various forms, either solely by hardware, solely by software, or through a combination thereof.

[0173] The aforementioned constituent elements include elements readily conceived by those skilled in the art, as well as substantially the same elements. Furthermore, the aforementioned structures can be appropriately combined. Additionally, various omissions, substitutions, or modifications to the structure are possible without departing from the spirit of the invention.

[0174] Symbol Explanation

[0175] 1 Display device

[0176] 10 Optical Path Control Device

[0177] 12 optical path control mechanisms

[0178] 12A Swinging Part

[0179] 12B actuator

[0180] 14 Control Circuit

[0181] 16. Drive Circuit (Drive Unit)

[0182] 17 vibration sensors

[0183] 18 Parameter Setting Section

[0184] 20. Optical Components (Optical Section)

[0185] 21 First Swinging Part

[0186] 22 Second Swing Section

[0187] 23 First shaft section

[0188] 24 Second Shaft

[0189] 25 First Actuator

[0190] 26 Second Actuator

[0191] 27 Support section

[0192] 31 First movable part

[0193] 32 Second movable part

[0194] 41, 44 coils

[0195] 42, 45 magnetic yoke

[0196] 43, 46 magnets

[0197] 100 Irradiation Device

[0198] AX First Swing Axis

[0199] BX Second Swing Axis

Claims

1. An optical path control device, comprising: The swinging part includes: an optical part for light incident; and a first swinging part for supporting the optical part. And a second swinging part, which is supported on a support part in a way that allows it to swing freely via a second shaft part, and the first swinging part is supported on the second swinging part in a way that allows it to swing freely via a first shaft part; The first actuator causes the swinging part to swing about the first shaft as a fulcrum and about the first swinging axis containing the first shaft as a center; as well as The second actuator causes the swinging part to swing about the second shaft as a fulcrum and around the second swinging axis, which includes the second shaft, as a center. The first swing axis intersects the second swing axis. The torsional stiffness of the second shaft is higher than that of the first shaft, so that the displacement time of the first swinging part and the displacement time of the second swinging part are the same.

2. The optical path control device according to claim 1, wherein, The torsional stiffness of the first shaft and the torsional stiffness of the second shaft are set so that the natural frequency of the first swinging part and the natural frequency of the second swinging part fall within a predetermined range.

3. The optical path control device according to claim 1 or 2, wherein, By making at least one of the cross-sectional area, length, and material of the first shaft portion and the second shaft portion different, the torsional stiffness of the second shaft portion is made higher than that of the first shaft portion.

4. The optical path control device according to claim 1 or 2, wherein, The light mentioned is the light used for imaging. The natural frequencies of the first oscillating part and the second oscillating part are set to values ​​that deviate from the frame rate of the corresponding image by an odd multiple.

5. The optical path control device according to claim 4, wherein, The natural frequency of the first swinging part and the natural frequency of the second swinging part are set to values ​​that are greater than n times the frame rate of the corresponding image and less than n+2 times the frame rate of the corresponding image, where n is an odd number.

6. The optical path control device according to claim 1, further comprising: The driving unit oscillates the oscillating unit by applying a waveform driving signal to the first actuator and the second actuator, thereby controlling the optical path of light transmitted through the optical unit. The waveform driving signal includes a first period for changing the current value and a second period for maintaining the current value. A vibration sensor detects the frequency of the oscillating part; as well as The parameter setting unit sets the drive signal of the waveform based on the frequency of the oscillating part detected by the vibration sensor.

7. A display device, comprising: The optical path control device according to any one of claims 1 to 6; as well as An irradiation device irradiates light onto the optical unit.

Images